A mod-chip will allow you to play UK games on a US machine, It would be a lot easier to sell the wii in the states, and buy a wii when you get there, that way, you can run it on a PAL T.V. and plug it into the UK power-grid with a lot less hassle. And no modding the wii and risking a brick.

Unfortunately, his US Wii will be NTSC standard, so it will only play NTSC games. The UK on the other hand, is PAL standard, so his US NTSC Wii will not play PAL games. Your only other choice is to mod the console, which I do not recommend because Nintendo are releasing updates to prevent the modded Wii consoles from functioning.